1. Field of the Invention
The present invention relates to a sheet feeding device for feeding a sheet one by one from loaded sheets and an image forming apparatus equipped with the sheet feeding device.
2. Description of the Related Art
Conventionally, an image forming apparatus that forms an image on a sheet includes a copying machine, a printer, and a facsimile machine. The copying machine is generally provided with a function for reading an image such as a document, converts the read image into electronic information, and forms an image on a sheet according to the electronic information. In recent years, there has been a copying machine provided with a communication function for receiving electronic information of images transmitted from an external device, and forms an image on a sheet according to the received electronic information of images.
A printer is generally provided with a function for forming an image on a sheet according to electronic information of an image transmitted from an external device, for example, a computer. Further, a facsimile machine is generally provided with a function for reading an image of a document or the like and for communication, and transmits the electronic information of the read image to an external device, and also forms an image on a sheet according to electronic information of an image transmitted from an external device.
In these image forming apparatuses, a sheet feeding device including a sheet accommodating unit that loads and accommodates sheets, and a sheet feeding unit that feeds the sheets from the sheet accommodating unit, is arranged at a lower part or a side part of an apparatus main body. The sheets are supplied from the sheet feeding device to the image forming unit, and images are formed on the sheets by the image forming unit.
In the sheet feeding device, when a sheet is fed from the sheet accommodating unit, it is necessary to prevent a skew of the fed sheet and a shift (lateral shift) in the sheet in a direction orthogonal to a sheet feeding direction of the sheet (hereinafter, referred to as a widthwise direction). For this reason, in the sheet accommodating unit, there is provided a pair of side edge regulating members that contact both side edges of the sheets for regulating a position in the widthwise direction of the sheets to be accommodated.
In the sheet accommodating unit that can accommodate a plurality of sizes of the sheets, the side edge regulating members are movably provided in the widthwise direction according to a size of the sheets to be accommodated.
In the so-called conveyance in the image forming apparatus with reference to the center, a sheet in any size is conveyed such that the center of the widthwise direction of the sheet coincides with the center of the widthwise direction of a conveyance path. In the image forming apparatus, in the so-called conveyance with reference to the center, a pair of the side edge regulating members is movable to be interlocked therebetween in order to improve operability.
A mechanism to effect for interlocking thereof generally uses a rack provided in each of the pair of side edge regulating members and a pinion that is in meshed engagement with each rack. With the configuration, when the one of the pair of side edge regulating members is moved, a rack of the pair of side edge regulating members causes the pinion to rotate, thereby causing the rack of the other side edge regulating member to move, and then causing in turn the other side edge regulating member to move.
In the sheet accommodating unit provided with the side edge regulating members with this configuration, after positions of the pair of the side edge regulating members are determined according to a size of the sheets, the pair of the side edge regulating members are locked by a locking mechanism so that the side edge regulating members do not move. Such a locking mechanism is generally configured such that the side edge regulating members are locked by causing ratchet teeth provided on the side edge regulating members, and urged by a spring to be engaged with rack gears fixed to the sheet accommodating unit.
In an image forming apparatus including such the side edge regulating members, and in which an insertion direction of the sheet accommodating unit into the apparatus main body and a feeding direction of a sheet from the sheet accommodating unit are orthogonal to each other, the following problem arises.
If the sheet accommodating unit with sheets is rapidly inserted into the apparatus main body, a shock is exerted from the sheets onto the side edge regulating members on a rear by the inertia of the sheets when the sheet accommodating unit stops. Accordingly, the side edge regulating members on the rear might be eventually displaced outwardly.
As a result, in some cases, the position of the sheets has been eventually shifted, causing a defective image in which positions of a sheet and an image are not correct, and the sheets have been skewed, causing a paper jam within the conveyance path. In particular, in the case of a sheet accommodating unit with a large accommodation volume of sheets, this problem noticeably occurs since an inertia force of the sheets is larger.
Thus, to solve this problem, it is necessary to ensure a locking of a locking mechanism of the side edge regulating members. For this reason, as discussed in Japanese Patent Application Laid-Open No. 9-110193, there is provided a locking mechanism in which by using a force when a sheet accommodating unit is mounted on an image forming apparatus main body, a pair of side edge regulating members are fixed by a frictional force induced by frictional members.
Further, as discussed in US Publication 2008/0251996, in a configuration in which side edge regulating members are moved by a plurality of racks and pinions, there is provided a locking mechanism in which gears are arranged coaxially with respect to the pinions, and then the side edge regulating members are locked by fixing the gears.
In a conventional configuration in which the side edge regulating members are locked for preventing the shift of the sheets, various parts have to be added, which causes a complicated configuration of the apparatus, and causes cost to increase.